FACIES ARCHITECTURAL ELEMENT AND DIAGENETIC OF MIDDLE MIOCENE NGRAYONG CLASTIC LIMESTONE AND SANDSTONE CASE STUDY DINGIL VILLAGE, JATIROGO, NORTH EAST JAVA BASIN, INDONESIA

The Oligocene and Miocene of East Java Basin provide an excellent chance to identify comparative response of clastic sandstone and clastic carbonate depositional system to eustatic and tectonic controls (Bransden and Mathew,1992). Depositional environment of Ngrayong Formation has been debate.

The research area is located in Dingil Village, Jatirogo which is show an excellent an outcrop in surface. Located within the Rembang Zone and northern of part Randublatung Zone appear of several an outcrop that show a difference of origin terrain. The Data was collected from field geological mapping and studio, laboratory analysis. Four significant sample and measure section from several data was collected. Petrography analysis has been done to determine porosity and permeability of each sample.

This paper will be describe the facies and diagenetic process of Ngrayong Formation from the petrography data. A description of diagenetic and facies of limestone and sandstone has been done. Composition of clastic limestone are fragment of clastic limestone which is composed by clastic limestone, coral fragment and fossil fragment with calcite associated micrite. There are several diagenetic event on the carbonate. Porosity of carbonate sample ranges among 10 % - 20 % . Sandstone was composed by fragment clastic sandstone (Medium Grain Sand - Fine Grain Sand) and micrite of mudstone with porosity 20 % - 30 % and fossil occurence. Several diagenetic process also found on sandstone's petrography analysis.

This study will bring us to another perspective of Ngrayong Formation which will be very usefull to hydrocarbon exploration.